The present invention generally relates to a method and an apparatus for cleaning a heater bellow in a chemical vapor deposition chamber more particular, relates to a method and an apparatus for cleaning a heater bellow by using a plug and a plug base for filling the bellow with an oxidizing fluid, rinsing the bellow with deionized water and then blow dry the bellow with an inert gas.
Chemical vapor deposition (CVD) technique has been broadly used in depositing semiconductor materials in the semiconductor fabrication technology. For instance, various layers of dielectric materials including those of silicon oxide can be deposited by the CVD technique. Since chemical vapor deposition is a process in which a film can be deposited by a chemical reaction or decomposition of a gas mixture at elevated temperatures on a wafer surface, typical CVD deposited films include single crystal silicon, polycrystalline silicon, silicon oxide, silicon nitride, phosphosilicate glass, borosilicate glass, borophosphosilicate glass, metals and metal compounds.
Chemical vapor deposition can be performed by various techniques including, but not limited to, high density plasma CVD, plasma enhanced CVD and sub-ambient CVD. The high density plasma CVD and the plasma enhanced CVD techniques utilized plasma ions to enhance the deposition rate and to reduce the deposition temperature for achieving obvious processing advantages. For instance, while silicon oxide can be deposited by a traditional CVD method at a temperature of 400xc2x0 C. or higher, the deposition temperature can be considerably reduced by the plasma enhanced CVD or high density plasma CVD techniques.
In a chemical vapor deposition chamber that is used for depositing silicon oxide, it is inevitable that silicon oxide particles or films are also deposited on the chamber interior away from the wafer surface. After repeated deposition processes are conducted in the chamber, residual oxide deposited on the chamber interior becomes a serious source of wafer contamination. Larger particles or thicker films of oxide tend to peel off from the chamber interior under high vacuum during the deposition process and fall onto the wafer surface. It is therefore necessary, as a preventive maintenance procedure, to clean the chamber interior after a pre-determined number of wafers have been processed in the chamber. One of the more advanced cleaning methods for the chamber interior is in-situ plasma cleaning such as by fluorine-containing etchant gas.
In the cleaning process for a chemical vapor deposition chamber by plasma ions of a fluorine-containing etchant, it is desirable that the endpoint of the cleaning process can be readily identified such that either under-cleaning or over-cleaning can be avoided. When the chamber interior is under-cleaned, particles or films left over may still present a contamination problem to the subsequent deposition process conducted in the chamber. When the chamber interior is over-cleaned, the corrosive etchant may damage the chamber interior and thus cause metal particle contamination. The ability to detect the endpoint of a chamber interior cleaning process is therefore an important requirement of the cleaning technique.
In a conventional cleaning process for plasma enhanced CVD or sub-ambient CVD, radio frequency is used as an energy source for generating plasma gas inside the chamber body, i.e. the plasma is generated in-situ. When the cleaning process is approaching an end, changes in the plasma radiation brightness can be readily used as an index of endpoint. However, in a high density plasma CVD chamber, microwave is used as the energy source for producing plasma ions outside the chamber body, i.e. plasma ions are produced ex-situ. When the cleaning process is approaching an end, any change in the plasma radiation brightness is barely detectable and thus, presenting great difficulties in identifying an endpoint of the cleaning process. As a result, when a high density plasma CVD chamber is cleaned, the cleaning process is normally time-controlled by a trial and error technique. The time-controlled cleaning method (i.e. or time mode) used conventionally is inadequate since it frequently results in over-cleaning of the deposition chamber and thus, damaging the chamber interior.
A particular part of the chamber where the heater is located, i.e. known as the heater bellow, is particularly difficult to clean due to its corrugated structure and its low position in the chamber. As a result, the heater bellow becomes a serious contamination source since deposition byproducts, and specifically metal particles such as W (tungsten) in a W CVD process tend to cumulate in the heater bellow. Conventionally, to clean the heater bellow, a multiplicity of chamber parts such as foreline valve, cooling fan, cylinder, pipes, cables, and hoses must all be removed before the heater bellow can be accessed and cleaned. The task of cleaning a heater bellow therefore requires two technicians working as long as two days to complete the cleaning process. Due to the time consuming nature of the cleaning process, the bellow cleaning is frequently skipped during a routine preventive maintenance procedure resulting in a serious contamination problem for the CVD chamber.
It is therefore an object of the present invention to provide a method for cleaning a heater bellow in a chemical vapor deposition chamber that does not have the drawbacks or shortcomings of the conventional methods.
It is another object of the present invention to provide a method for cleaning a heater bellow in a chemical vapor deposition chamber by providing a specially designed cleaning apparatus and mounting the apparatus in the chamber.
It is a further object of the present invention to provide a method for cleaning a heater bellow in a chemical vapor deposition chamber by first exposing the bellow to an oxidizing fluid and then rinsing the bellow with deionized water.
It is another further object of the present invention to provide a method for cleaning heater bellow in a chemical vapor deposition chamber by first mounting a specially designed cleaning apparatus inside the heater bellow, filling the bellow with an oxidizing fluid, rinsing the bellow with deionized water and then drying the bellow with an inert gas.
It is still another object of the present invention to provide an apparatus for cleaning a heater bellow in a chemical vapor deposition chamber which includes a plug and a plug base for use as a cleaning tool when mounted in the heater bellow.
In accordance with the present invention, an apparatus and a method for cleaning a heater bellow in a chemical vapor deposition chamber are provided.
In a preferred embodiment, an apparatus for cleaning a heater bellow in a chemical vapor deposition chamber is provided which includes a plug of elongated shape that has a hollow fluid passageway therethrough, the plug has a quick connect fitting on the top end and a threaded pipe fitting at a bottom end, the plug further has a plurality of apertures located in a bottom half of the plug in fluid communication with the hollow fluid passageway; and a plug base that has an inside threaded hole for threadingly engaging the bottom end of the plug and for draining away a fluid from a drain pipe in fluid communication with the inside threaded hole, the plug base further has an outside peripheral surface adapted for fitting intimately into a bottom cavity for the heater bellow.
In the apparatus for cleaning a heater bellow in a chemical vapor deposition chamber, the bottom end of the plug is further equipped with an O-ring for sealingly engaging the inside threaded hole in the plug base. The plug base may be formed in a cylindrical shape which has an inside diameter for the inside threaded hole and an outside diameter defining the outside peripheral surface, the outside peripheral surface of the plug base may be further equipped with a O-ring for sealingly engaging the bottom cavity for the heater bellow. The plug and the plug base may be fabricated of a rigid plastic or metal, or fabricated of aluminum.
The present invention is further directed to a method for cleaning a heater bellow in a chemical vapor deposition chamber which can be carried out by the operating steps of providing a cleaning apparatus that consists of a plug of elongated shape that has a hollow fluid passageway therethrough, the plug has a quick connect fitting on a top end and a threaded pipe fitting at a bottom end, the plug further has a plurality of apertures located in a bottom half of the plug in fluid communication with the hollow fluid passageway, and a plug base that has an inside threaded hole for threadingly engaging the bottom end of the plug and for draining away a fluid from a drain pipe in fluid communication with the inside threaded hole, the plug base further has an outside peripheral surface adapted for fitting intimately into a bottom cavity for the heater bellow; mounting the cleaning apparatus into the bottom cavity of the heater bellow; filling through the top end of the plug an oxidizing fluid into the heater bellow and soaking for a sufficient length of time until substantially all residue on an interior wall of the bellow is oxidized; removing the oxidizing fluid from the heater bellow by draining through the drain pipe; filling through the top end of the plug deionized water into the heater bellow and purging an inert gas through the ionized water; removing the deionized water from the heater bellow by draining through the drain pipe; and filling through the top end of the plug an inert gas or air into the heater bellow to substantially dry the interior wall of the bellow.
The method for cleaning a heater bellow in a chemical vapor deposition chamber may further include the step of wiping the interior wall of the bellow with a lint-free cloth after the deionized water is removed from the heater bellow. The method may further include the step of flowing into the heater bellow to substantially dry the interior wall of the bellow. The method may further include the step of mounting the cleaning apparatus into the bottom cavity of the heater bellow by frictionally engaging an O-ring to an inside wall of the bottom cavity of the bellow, or the step of soaking the interior wall of the heater bellow with the oxidizing fluid for a time period of at least 15 min, or the step of soaking the interior wall of the heater bellow with H2O2, or the step of soaking the interior wall of the heater bellow with H2O2 for at least 20 min. The method may further include the step of repeating the filling/removing steps for the oxidizing fluid and the deionized water at least once prior to the drying step by inert gas or air. The method may further include the step of purging Ar gas through the deionized water for at least 10 min, or the step of flowing into the heater bellow N2 gas for drying the interior wall of the bellow, or the step of flowing into the heater bellow N2 gas for at least 20 min. for drying the interior wall of the bellow.